Methods and apparatus' pertaining to the technical field initially mentioned are known. U.S. Pat. No. 5,205,845 of the Regents of the University of Michigan for example describes an apparatus and a method for gas chromatography with more than one separation column having different separation characteristics. The sample is injected with an injection sequence into these columns and the analyte eluted from the columns is measured with a shared detector to obtain a composite of the outputs from the columns. This composite is a single chromatogram which provides a good resolution of all components of interest because the characteristics of the columns and the injection sequence are chosen so that significant peaks can be superimposed relative to the output of the other columns. In order to achieve this, the portions of a single column chromatogram which are ordinarily free of peaks are used to insert peaks from another column related to specific compounds of interest.
Similarly, US 2009/0250607 A1 of Phoenix S&T Inc. discloses an apparatus and a method for liquid chromatography with more than one liquid chromatography column and a mass spectrometer as shared detector. In this case, the number of columns and spray devices employed is a number at which a cyclic Hadamard simplex matrix exists. To the end of each column, a separate sample spraying device is connected. These spraying devices are positioned aiming at the mass spectrometer inlet and spray when a high voltage is applied. When operated, the high voltage is applied in different Hadamard sequences to the different spraying devices such that each spray device sprays only during the “on” state of the respective Hadamard sequence when the high voltage is applied and stops spraying during the “off” state of the respective sequence. During one peak in the chromatogram of a column, an entire Hadamard-Sequence is applied to the spray device of the respective column. In the signal measured by the mass spectrometer, the column from which the signal originates can be identified because of a missing signal at a particular time in the Hadamard sequence.
The disadvantage of the apparatus' and methods described in U.S. Pat. No. 5,205,845 and US 2009/0250607 A1 is that a lot of time is required for obtaining a full chromatogram which comprises the information of the chromatograms of the individual separation columns.
Another apparatus and method where this disadvantage is at least partially overcome is described in U.S. Pat. No. 5,492,838 of Pawliszyn. In this example, the substances are extracted from a liquid phase in a gas chromatography column by single or multiple cooling or heating pulses. These pulses may be of random sequence. After having measured the extracted substances with a detector, the obtained signal is deconvoluted with a cross-correlation, a Fourier transform or a Hadamard transform in order to obtain a continuous analysis of the extracted substances. However, this example has the disadvantage that a measurement can only be obtained for one column at a time.